On the picture: The northern side of the prayer hall, with the muqarnas (stalactite) vaulting above the entrance, and the ‘Müezzin Mahfili’ /platform for the muezzin (the man who recites the call to prayer).
Apart from calling the congregation to prayer, in some mosques the muezzin stands during the worship service on his special platform (in this mosque: a loge) and gives responses during the imam's sermon.

Note also the muqarnas decoration on the bases of the pendentives that connect the dome to the pillars which support it.

Correspondent: J.M.Criel, Antwerpen.
Sources: Website of ‘diyarbakirmuftulugu.gov.tr’ & Vikipedia.